Make the repeating argument to timers optional.

samples/chat/chat_server_lib.dart

Index: samples/chat/chat_server_lib.dart
diff --git a/samples/chat/chat_server_lib.dart b/samples/chat/chat_server_lib.dart
index 883214c3104521337ddb48028c94e222f7fa7eca..97242aa73dc1dc2ade52a55cb4774529399f1707 100644
--- a/samples/chat/chat_server_lib.dart
+++ b/samples/chat/chat_server_lib.dart
@@ -591,7 +591,7 @@ class IsolatedServer extends Isolate {
 
     // Start a timer for cleanup events.
     _cleanupTimer =
-        new Timer((timer) => _topic._handleTimer(timer), 10000, true);
+        new Timer.repeating((timer) => _topic._handleTimer(timer), 10000);
 
     // Start timer for periodic logging.
     void _handleLogging(Timer timer) {
@@ -619,7 +619,7 @@ class IsolatedServer extends Isolate {
                       _requestReceivedHandler(req, rsp),
                   backlog: message.backlog);
               replyTo.send(new ChatServerStatus.started(_server.port), null);
-              _loggingTimer = new Timer(_handleLogging, 1000, true);
+              _loggingTimer = new Timer.repeating(_handleLogging, 1000);
             } catch (var e) {
               replyTo.send(new ChatServerStatus.error(e.toString()), null);
             }